The advantageous or promoting effects of adding a second metal on supported cobalt and nickel catalysts have been reported in a number of studies. For example, higher carbon oxides hydrogenation activity, better active phase reducibility, and higher catalyst stability are some of the advantages of these promoter additions. Also, the promoters lower the temperature for the reduction of cobalt and nickel oxides to metallic cobalt and nickel, by the well-known mechanism of hydrogen spillover. Furthermore, the addition of small amounts of promoters to catalysts increases the dispersion and reducibility of active metals and achieves improved reaction conversion and selectivity.
Current promoted cobalt and nickel catalysts for carbon oxides hydrogenation are prepared by a traditional impregnation method. However, the preparation of promoted catalysts using these traditional or prior art impregnation methods may result in the promoters impregnating or depositing on both the active phase and the support.
Therefore, there is a present need for a technique to preferentially deposit promoters onto the catalyst active phase, with minimal or no deposition onto the support therefor. As a result, the highest promoting role of the second metal occurs when the promoter is only impregnated onto the cobalt or nickel active phase with close contacts, but not onto the support surface, which undermines the product.
It is, accordingly, an object of the present invention to provide an improved technique and method for the selective deposition of nobler metals onto the active phase components to the exclusion of the supports therefor.
This and other objects are met in various embodiment of the present invention where techniques are described that implement the focused deposition of the noble metals onto the active phase portions, offering significant advantages over the known prior art which are unable to do this.